My experience with the power tube vs preamp tube...
I owned an early '70s Music Man HD-130 Reverb with a 2 x 12 cab for a number of years, and recently traded it off towards something I could actually carry around.
The MM was an early hybrid: solid state pre with a tube power amp, 130 watts. They were famous for never distorting. It wasn't possible to play them loudly enough for the power tubes to break up. It was known as the King of Loud Clean back in the '70s for that reason.
Like I said, mine was an early one, and it had a 12AX7 as a phase inverter tube in the pre. Without that tube, it would never distort: if you cranked the volume on the pre you could get nice controllable distortion at any level by using the master volume. If the pre wasn't turned over half way, it would not distort.
In contrast, my '63 Sears Silvertone Twin Twelve will distort at 10 o'clock on the volume knob, and sweet it is, too.
But I have two new amps, both bought since July 1:
a Fender Jazzmaster Ultrallight solid state amp, and a Hot Rod Blues Jr NOS (tweed, tube rectifier and Jensen speaker). Each one kills, in its own way: the JM is more like the Deluxe Reverb reissue (but livelier sounding, to my ear) while the Blues Jr is chimey-er and more like the older Fenders.
Another way to put it is that the Jazzmaster is a great ensemble amp, and the Blues Jr excells at solo guitar, where you want a sound with more depth.
The JM doesn't lack for distortion horsepower. I play my Les Paul Deluxe through it on the Clean channel and my Epiphone Sheraton II (both with SD pickups) through the Drive channel and each one sounds terrific. It's a compressed, focused sound, while the Blues Jr sounds richer and has more highs.
The main drawback to the Jazzmaster is that it's close to $1100; the Blues Jr is $550, or right at half. But I love having them both. If you're on a budget, obviously, the Blues Jr would be the way to go; otherwise, if I could only have one, I'd take the JM.